A Randomized Clinical Trial of a Standardized Pumpkin-Seed-Derived Peptide Extract: Body Composition Outcomes and Exploratory Analysis by Baseline Adiposity in Overweight Adults.
Lin Y, Chung W, Lin Y, Hsu P • International journal of molecular sciences • 2026
In a 12-week randomized, double-blind, placebo-controlled trial, a standardized pumpkin-seed-derived peptide extract (IRK-19®, 600 mg/day) did not produce statistically significant improvements in body weight, BMI, or adiposity outcomes in the overall overweight adult population, though post hoc subgroup analyses suggested potential effects in participants with higher baseline fat mass.
Key Findings
Results
The overall study population showed no statistically significant between-group differences in body weight, BMI, or adiposity-related outcomes at Week 12.
The trial enrolled 50 overweight adults in a 12-week, randomized, double-blind, placebo-controlled design.
48 participants had evaluable DXA data at Week 12.
Participants received either IRK-19® at 600 mg/day or placebo.
Between-group comparisons of body weight, BMI, and adiposity-related outcomes did not reach statistical significance in the overall study population.
Results
In a post hoc subgroup of participants with baseline total fat mass ≥28.4 kg, IRK-19® was associated with significantly greater reductions in body weight and BMI compared to placebo.
The subgroup was defined by baseline total fat mass ≥28.4 kg, representing the study-specific 75th percentile (n = 13).
Adjusted between-group difference for body weight was -2.30 kg (95% CI, -4.08 to -0.51; p = 0.018).
Adjusted between-group difference for BMI was -0.75 kg/m² (95% CI, -1.48 to -0.02; p = 0.045).
These findings were post hoc and not adjusted for multiple comparisons.
Results
In the high-baseline-fat-mass subgroup, the adjusted between-group difference in total fat mass was -1.60 kg, which did not reach statistical significance.
Adjusted between-group difference for total fat mass was -1.60 kg (95% CI, -3.23 to 0.04; p = 0.055) in the subgroup with baseline total fat mass ≥28.4 kg (n = 13).
This finding was also post hoc and not adjusted for multiple comparisons.
The result narrowly missed the conventional threshold for statistical significance.
Results
Treatment-by-baseline-fat-mass interaction effects did not reach statistical significance for any of the primary adiposity outcomes.
Interaction p-values were p = 0.065 for body weight, p = 0.106 for BMI, and p = 0.057 for total fat mass.
None of the treatment-by-baseline-fat-mass interactions reached conventional statistical significance (p < 0.05).
This limits conclusions about whether baseline fat mass truly modifies treatment response.
Methods
The standardized clinical preparation (IRK-19®) contained 66.2% crude protein, with specific peptide fractions and markers characterized by SEC-UV and HPLC.
Components with apparent molecular weights ≤6.29 kDa accounted for 23.6% of the total SEC-UV chromatographic area.
The combined HPLC-measured content of six selected peptide markers was 2.79% (w/w).
The dose administered was 600 mg/day.
The preparation was derived from pumpkin seeds.
Results
Individual metabolic laboratory abnormalities were observed and identified as warranting further assessment in future prospective trials.
The abstract notes that individual metabolic laboratory abnormalities warrant further assessment.
No specific details about the nature or frequency of these abnormalities are provided in the abstract.
The authors indicate these findings should be evaluated in future prospectively designed trials.
Conclusions
The authors concluded that prospectively designed trials with prespecified adiposity strata are needed to determine whether baseline fat mass is associated with differential treatment response.
The post hoc subgroup findings were explicitly stated to 'warrant further investigation' but were not adjusted for multiple comparisons.
The subgroup analysis was not prespecified, limiting its inferential value.
The authors call for trials with prespecified adiposity strata to properly test the hypothesis of effect modification by baseline fat mass.
What This Means
This research tested whether a supplement made from pumpkin seed peptides (called IRK-19®, taken at 600 mg per day) could help overweight adults lose body fat over 12 weeks. The study was well-designed — it was randomized, double-blind, and placebo-controlled, meaning neither participants nor researchers knew who was getting the real supplement versus a dummy pill. When the researchers looked at all 48 participants with complete data, they found no statistically significant differences between the supplement and placebo groups in body weight, BMI, or body fat measurements.
However, when the researchers conducted an additional, unplanned (post hoc) analysis focusing only on the 13 participants who started the study with the highest body fat levels (above the 75th percentile for the group, or roughly 28.4 kg of total fat mass), those taking IRK-19® lost on average about 2.3 kg more body weight and 0.75 kg/m² more BMI than those on placebo, and these differences were statistically significant. The reduction in total fat mass in this subgroup (-1.60 kg) narrowly missed statistical significance. Importantly, statistical tests for whether baseline fat mass actually changed how well the supplement worked did not reach significance either, meaning it is unclear whether people with more fat truly respond differently to the treatment.
This research suggests that pumpkin-seed-derived peptide extracts do not broadly help overweight adults lose weight, but raises the possibility — not yet confirmed — that people with higher baseline body fat might respond differently. Because the subgroup findings were unplanned, involved a small number of participants, and were not corrected for multiple statistical tests, they should be interpreted with caution. The authors themselves call for larger, better-designed trials that plan in advance to look at participants with different fat levels to properly answer whether baseline adiposity influences who might benefit from this type of supplement.
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Lin Y, Chung W, Lin Y, Hsu P. (2026). A Randomized Clinical Trial of a Standardized Pumpkin-Seed-Derived Peptide Extract: Body Composition Outcomes and Exploratory Analysis by Baseline Adiposity in Overweight Adults.. International journal of molecular sciences. https://doi.org/10.3390/ijms27198813